A vehicle air-conditioning system provided with a heat exchanger for the exchange of heat between inside air and outside air when the outside air is being introduced into a passenger compartment and the inside air is being discharged from within the passenger compartment is disclosed in Japanese Patent Laid-Open Publication No. 2002-200916, for example. This air-conditioning system will be described with reference to FIG. 10.
In an air-conditioning unit 100 shown in FIG. 10, a blower fan 101 is rotated and the opening and closing of first and second introduction doors 102, 103 is controlled, whereby outside air and inside air (hereinafter referred to as “introduced air”) are delivered to the blower fan 101.
The introduced air is delivered to an evaporator 105 by the blower fan 101 so that the introduced air is cooled and dehumidified by the evaporator 105.
Part of the cooled and dehumidified introduced air is heated by a heater core 106 and delivered to a mixing chamber 107. The other part of the introduced air is directly delivered through an opening 108a of a mixing door 108 into the mixing chamber 107. The two flows of the introduced air are mixed in the mixing chamber 107 and adjusted to a desired temperature.
The introduced air adjusted to the desired temperature is discharged through, for example, a third passage 114 by opening, among first, second and third outlet doors 111, 112 and 113, the third outlet door 113, and through an outlet (not shown) into a passenger compartment.
The air-conditioning unit 100 is provided with an inside air discharge passage 118 which communicates with the passenger compartment, and an outside air introduction passage 119 upstream of the blower fan 101.
Inside air introduced from an inlet 118a of the inside air discharge passage 118 is delivered through a heat exchanger 120 to an outlet 118b of the inside air discharge passage 118.
The inside air passing through the outlet 118b of the inside air discharge passage 118 is discharged through a passage 122 formed in a door 121 and through an inside air discharge opening 122a to the outside.
When outside air introduced from an outside air inlet 119a is delivered through the heat exchanger 120 and through the outside air introduction passage 119 to the blower fan 101, the outside air exchanges heat with inside air delivered to the heat exchanger 120, being warmed by the heat of the inside air. Thus, the outside air is increased in temperature utilizing the heat of the inside air discharged from the passenger compartment, and the outside air having the increased temperature is delivered to the blower fan 101, resulting in an increased effect of heating.
However, a common vehicle is provided with an air outlet valve for discharging air in a lower area of a trunk for maintaining a desired internal pressure in a passenger compartment. As the air outlet valve, a louvered one is known, for example. When the internal pressure in the passenger compartment is not as high as a specified value, the air outlet valve keeps the louver closed by a spring force of an elastic member. When the internal pressure in the passenger compartment rises to the specified value, the internal pressure exceeds the spring force, opening the louver against the spring force of the elastic member. Inside air in the passenger compartment is discharged from the opening of the louver to the outside.
When inside air in the passenger compartment is discharged from the opening of the louver to the outside as described above, the heat of the inside air is released outside from the opening of the louver. The heat released outside from the opening of the louver cannot be utilized as heat for increasing the temperature of outside air introduced into the air-conditioning unit 100.
It is thus desired that an air-conditioning system allowing for an efficient exchange of heat between inside air discharged from within a passenger compartment and outside air introduced into an air-conditioning unit come into practical use.